1. Field of the Invention
The present invention relates to a dye and an ink containing such a dye, and particularly to a dye and an ink suitable for ink-jet uses, and an ink-jet recording method using such an ink and ink-jet instruments containing the ink therein.
2. Related Background Art
In recent years, the developments of color displays in personal computers from the desktop type to the note type have been advanced. Application software for making good use of color's power of expression has been published. Therefore, color recording by printers is a promising field.
Among various recording processes used in these printers, an ink-jet recording process is a process in which droplets of an ink are formed by any of various ink-ejection systems, and they are applied to a recording medium such as plain paper, converted paper, plastic film, or a cloth to conduct recording. The process has advantages that a recording apparatus making good use of such a process is silent because a recording head makes no contact with a recording medium, printing can be conducted at high speed, and color recording can be achieved with ease.
Inks used in ink-jet recording have heretofore been required to have the following properties:
(1) providing images sufficient in optical density;
(2) providing recorded images on which feathering scarcely occurs;
(3) providing recorded images which do not run even when brought into contact with water (water fastness);
(4) providing recorded images excellent in light fastness;
(5) causing no clogging at an orifice;
(6) undergoing no change of properties even after stored for a long period of time;
(7) being high in safety upon their use; and
(8) exerting no adverse influence on means for generating thermal energy in an ink-jet system making good use of thermal energy.
Inks used in an ink-jet recording process for conducting color recording are also required in addition to the above properties to have the following properties:
(9) being high in color purity in individual inks and capable of reproducing color tone faithful to the original; and
(10) even when stopping ejection of an ink of a specific color from a nozzle for a predetermined period of time to use it in a part of a print to be produced, causing no ejection failure upon resumption of the ejection.
These properties or characteristics may of course be influenced by the composition of ink, and are also greatly controlled by the nature of a dye contained as a coloring material in the ink. It is difficult to satisfy all the above performance requirements by using existing dyes.
The conventional water-based inks for ink-jet recording have principally used existing water-soluble dyes. These dyes each have a sulfonic group as a solubilizing group, and hence are highly solubile in media for water-based inks, and the long-term storability of inks containing such a dye is also generally good. However, a print obtained by making a record with such an ink on a recording medium has undergoes running of the dye and bleeding when splashed with water or touched with wet fingers, or when characters on the print are rubbed with a water-based felt pen, so that the print is often deteriorated in image quality and made illegible. In particular, this phenomenon is more marked on color inks because dyes used in the color inks are lower in affinity for paper than black dyes. This problem has been included among problems offered upon the formation of color images on plain paper.
Japanese Patent Application Laid-Open No. 55-152766 discloses an ink intended to improve solution stability, long-term storability and ejection stability using a yellow dye having a specific molecular-structure. However, the problem of water fastness as described above has not yet been fully solved even by this ink.
Japanese Patent Publication No. 5-426 discloses an ink containing a yellow dye having a specific molecular structure, the ink being intended to improve the water fastness of the resulting print by printing on specially treated paper with the ink. However, it is demonstrated by examples of the publication that this ink has no effect on commercially available plain paper.
Japanese Patent Publication No. 2-5785 discloses an ink containing C.I. Direct Yellow 86. However, the hue of this dye is somewhat reddish-yellow and hence involves a problem from the viewpoint of color reproducibility.